Seal for a turbine system

ABSTRACT

A seal for a turbine system includes a rotor, a bowl region and a stator assembly having a tip strip disposed proximate the rotor. Also included is a packing head disposed proximate the tip strip. Further included is a flex seal having a first end portion fixedly secured to at least one of the tip strip and the packing head, with a second end portion slidably engaged with at least one of the tip strip and the packing head.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to turbine systems, and moreparticularly to a seal for such turbine systems.

Turbine systems, such as steam turbine systems, for example, ofteninclude different sections that operate at various pressures, includinga high pressure (HP) section and an intermediate pressure (IP) section,each housing a portion of a rotor. During operation, it is common for acooling source to be introduced to the area of the IP section proximatethe rotor, in order to maintain the temperature of the rotor below thetemperature of the general IP section. Failure to achieve maintenance ofthe rotor surface at a cooler temperature results in a need to reducethe rotor diameter design, but the reduced diameter negatively impactsoverall steam turbine system performance.

Steam from the HP section often leaks across packing, such as N2packing, toward the lower pressure environment of the IP section, andmay provide the cooling source for the rotor. Preventing a separatesteam source, namely the relatively hot IP section steam, from reachingthe rotor surface requires sealing between stators proximate the rotorsurface. Previous efforts to seal such locations from the hot IP sectionsteam have encountered issues with radial and axial displacement of thestators during operation of the steam turbine system, with which theseals are often in contact.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, a seal for a turbine systemincludes a rotor, a bowl region and a stator assembly having a tip stripdisposed proximate the rotor. Also included is a packing head disposedproximate the tip strip. Further included is a flex seal having a firstend portion fixedly secured to at least one of the tip strip and thepacking head, with a second end portion slidably engaged with at leastone of the tip strip and the packing head.

According to another aspect of the invention, a seal for a steam turbinesystem includes a rotor, a bowl region and a stator assembly including astator tip strip, wherein the stator tip strip is disposed proximate therotor. Also included is a first steam source injected into the bowlregion at a first temperature. Further included is a packing headdisposed proximate the stator tip strip. Yet further included is a rotorcooling steam source injected at a second temperature along a path inclose proximity to the rotor, wherein the second temperature is lowerthan the first temperature. Also included is a flex seal having a fixedportion and a free portion, wherein the flex seal is fixedly coupled atthe fixed portion to at least one of the stator assembly, the packinghead and the stator tip strip, wherein the flex seal prevents the firststeam source from entering the path in close proximity to the rotor.

According to yet another aspect of the invention, a seal for a steamturbine system includes an intermediate pressure section having a rotor,a bowl region, an outer casing and a stator assembly having a tip stripdisposed proximate the rotor, wherein the intermediate pressure sectioncomprises an axial direction corresponding to a longitudinal directionof the rotor and a radial direction extending relatively from the rotorto the outer casing. Also included is a packing head disposed proximatethe tip strip. Further included is a flex seal having a first endportion fixedly secured to at least one of the tip strip and the packinghead, with a second end portion slidably engaged with at least one ofthe tip strip and the packing head and configured to be displaced in theaxial direction and the radial direction.

These and other advantages and features will become more apparent fromthe following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWING

The subject matter, which is regarded as the invention, is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 is a schematic illustration of a steam turbine system;

FIG. 2 is a cross-sectional view of an inlet region of an intermediatepressure section of the steam turbine system illustrating a flex sealaccording to one embodiment;

FIG. 3 is a cross-sectional view of the flex seal illustrated in FIG. 2;

FIG. 4 is a cross-sectional view of the flex seal according to a secondembodiment;

FIG. 5 is a cross-sectional view of the flex seal according to a thirdembodiment; and

FIG. 6 is a cross-sectional view of the flex seal according to a fourthembodiment.

The detailed description explains embodiments of the invention, togetherwith advantages and features, by way of example with reference to thedrawings.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a turbine system and more specifically anopposed-flow steam turbine system is generally illustrated with thereference numeral 10. The steam turbine system 10 includes a highpressure (HP) section 12 and an intermediate pressure (IP) section 14,with the HP section 12 being defined by an HP casing 16, and similarlythe IP section 14 being defined by an IP casing 18. A central section 20disposed between the HP section 12 and the IP section 14 includes a highpressure steam inlet 22 and an intermediate pressure steam inlet 24.

An annular section divider 26 extends radially inwardly from the centralsection 20 towards a rotor 28 that extends between the HP section 12 andthe IP section 14. More specifically, the annular section divider 26extends circumferentially around a portion of the rotor 28 between an HPsection inlet nozzle 30 and an IP section inlet nozzle 32. The annularsection divider 26 has a packing structure 50 annularly fitted close tothe rotor 28.

In operation, the high pressure steam inlet 22 receives high pressure,high temperature steam from a steam source, such as a boiler (notillustrated), for example. Steam is routed through the HP section 12from the first HP section inlet nozzle 30, from which work is extractedfrom the steam to mechanically rotate the rotor 28 via a plurality ofturbine blades 27, or buckets (shown in FIG. 2) which are operablycoupled to the rotor 28. Each set of buckets includes a correspondingstator 29 (shown in FIG. 2) that facilitates routing of steam to theassociated buckets. The steam exits the HP section 12 and is returned tothe boiler, where the steam is then reheated. The reheated steam is thenrouted to the intermediate pressure steam inlet 24 and returned to theIP section 14 via the IP section inlet nozzle 32 at a reduced pressurethan steam entering the HP section 12, but at a temperature that isapproximately equal to the temperature of the steam entering the HPsection 12. Work is extracted from the steam in the IP section 14 in asimilar manner as that employed for the HP section 12 via a system ofrotating and stationary components. Accordingly, an operating pressurewithin the HP section 12 is higher than an operating pressure within theIP section 14, such that steam within the HP section 12 tends to flowtowards the IP section 14 through leakage paths that may develop betweenthe HP section 12 and the IP section 14.

Although the steam turbine system 10 has been described as anopposed-flow high pressure and intermediate pressure steam turbinecombination, it is to be appreciated that the steam turbine system 10may be employed with any individual turbine including, but not limitedto, low pressure turbines. Additionally, the steam turbine system 10 isnot limited to being configured as an opposed-flow steam turbine, butmay instead be configured as a single-flow or double-flow steam turbinesystem, for example. Moreover, it is contemplated that embodimentsdisclosed herein may be used in conjunction with gas turbine systems aswell.

Referring to FIG. 2, a cross-sectional portion of the IP section 14 isshown in greater detail. The IP section 14 includes an IP bowl 40proximate the IP section inlet nozzle 32, wherein a stream 42 of hightemperature, intermediate pressure steam is injected into the IP bowl 40for routing through the IP section 14, as described above. The stator 29within the IP section 14 is operably connected at a radially outwardposition to the IP casing 18 and includes a tip strip 46 that isdisposed proximate the rotor 28. Adjacent to, and in close proximitywith, the tip strip 46 of the stator 29 is a packing head 48 of thepacking structure 50 disposed between the HP section 12 and the IPsection 14. In order to maintain the rotor 28 at a suitable applicationtemperature, a cooling source may be introduced proximate the rotor 28.Such a cooling source may comprise a leaked flow 52 from the HP section12 that has leaked across the N2 packing structure 50. The leaked flow52 that comprises high pressure steam from the HP section 12 naturallytends to flow in the direction of the lower pressure IP section 14. Asthe leaked flow 52 travels from the HP section 12 to the IP section 14,the temperature of the leaked flow 52 decreases, thereby providing acooler flow to the rotor 28 than would otherwise be felt by the rotor 28as a result of heat transfer stemming from the stream 42 generallyflowing through the IP section 14. It is to be appreciated that thecooling source has been described as the leaked flow 52 from the HPsection 12 across the N2 packing structure 50, however, variousalternative cooling sources may be employed to maintain the temperatureof the rotor 28 below that of the general IP section 14.

As illustrated, a gap 54 between the packing head 48 and the tip strip46 of the stator 29 is present. Unsealed, the gap 54 may result in adirect path of the stream 42, which may have a varying temperature ofabout 1,100° F., toward the rotor 28. Additionally, mixing of the stream42 with a cooling source, such as the leaked flow 52, hinders theefficiency of the rotor cooling effort. In order to prevent passage ofthe stream 42 through the gap 54, a flex seal 60 is disposed within thegap 54. The flex seal 60 includes a first end portion 62 and a secondend portion 64, with one of the first end portion 62 or the second endportion 64 being operably coupled to the tip strip 46, or more generallythe stator 29, or the packing head 48. The end not operably coupled toan object, that being either the first end portion 62 or the second endportion 64 is fittingly engaged with either the tip strip 46 or thepacking head 48 and relatively free to displace. In other words,irrespective of whether the first end portion 62 or the second endportion 64 is operably coupled to the tip strip 46 or the packing head48, the other end is fittingly engaged with the other object,specifically the tip strip 46 or the packing head 48.

The ability of the first end portion 62 or the second end portion 64 todisplace is based on the tendency of stator components, such as the tipstrip 46 and the packing head 48 to displace in an axial and/or a radialdirection during operation of the steam turbine system 10. Therefore,tight seals having a pressure fit at both the first end portion 62 andthe second end portion 64 or an operable connection at the first endportion 62 and the second end portion 64 are not adequately held withinthe gap 54. The allowance of the flex seal 60 to displace proximate atleast one end in correspondence with an associated structure, such asthe tip strip 46 or the packing head 48, maintains a robust seal of thegap 54, while accommodating the axial and/or radial displacement of thetip strip 46 or the packing head 48.

Referring to FIGS. 3-6, enlarged views of various embodiments of theflex seal 60 are illustrated. It is to be appreciated that thegeometries of the flex seal 60 shown are merely illustrative, and arenot limiting, as numerous geometric variations of the flex seal 60 arecontemplated. Irrespective of the specific geometry employed for theflex seal 60, included is the first end portion 62 and the second endportion 64, with each being disposed in contact with the tip strip 46and the packing head 48, respectively. As previously described, only oneend of the flex seal 60 is operably coupled to one of the tip strip 46and the packing head 48. By way of example, the first end portion 62 maybe operably coupled to the tip strip 46 via mechanical fastening, suchas bolting, riveting, or welding. These manners of mechanicallyfastening the first end portion 62 to the tip strip 46 are merelyexamples, and any suitable fastener may be employed to ensure retentionof the first end portion 62 to the tip strip 46. Continuing with theexample, the second end portion 64 is in fitting engagement with thepacking head 48, yet not operably coupled in a fixed manner, such thatdisplacement may be achieved during axial and/or radial displacement ofthe tip strip 46 and/or the packing head 48. Adequate sealing andengagement of the second end portion 64 with the packing head 48 isachieved by pre-pressurizing the flex seal 60 to maintain sealing duringeven relatively large displacements.

The various embodiments of the flex seal 60 are illustrated and may becharacterized as “Y-shaped” (FIG. 3), “S-shaped” (FIG. 4), or variationsthereof (FIGS. 5 and 6). While described as having the first end portion62 and the second end portion 64 that are either operably coupled or infitting engagement with the associated structural components, it is tobe appreciated that the end is not necessarily the portion that requiressuch a connection. As seen in FIG. 6, for example, the second endportion 64 is not disposed in contact with the packing head 48, and assuch it may be another portion of the flex seal 60 that provides theoperable connection or the fitting engagement. As described above, theillustrated embodiments of the flex seal 60 are merely examples of thenumerous contemplated configurations that may be employed to prevent thehigh temperature steam, in the form of the stream 42, from intruding therotor area through the gap 54.

Advantageously, the flex seal 60 prevents the high temperature steamrouting through the IP section 14 from being imposed on the surface ofthe rotor 28, while maintaining adequate structural integrity at sealcontact points.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

1. A seal for a turbine system comprising: a rotor, a bowl region and astator assembly having a tip strip disposed proximate the rotor; apacking head disposed proximate the tip strip; and a flex seal having afirst end portion fixedly secured to at least one of the tip strip andthe packing head, with a second end portion slidably engaged with atleast one of the tip strip and the packing head.
 2. The seal of claim 1,wherein the flex seal is disposed in an intermediate pressure section ofthe turbine system.
 3. The seal of claim 1, wherein the first endportion is bolted to the tip strip.
 4. The seal of claim 1, wherein thefirst end portion is riveted to the tip strip.
 5. The seal of claim 1,wherein the first end portion is welded to the packing head.
 6. The sealof claim 2, wherein the stator assembly is operably coupled to an outercasing of the intermediate pressure section.
 7. The seal of claim 6,further comprising an axial direction and a radial direction, whereinthe axial direction relatively corresponds to a longitudinal directionof the rotor and the radial direction relatively extends from the rotorto the outer casing.
 8. The seal of claim 7, wherein the second endportion of the flex seal is configured to be displaced in the axialdirection and the radial direction.
 9. The seal of claim 1, wherein theflex seal is of a relatively Y-shaped geometric configuration.
 10. Aseal for a steam turbine system comprising: a rotor, a bowl region and astator assembly including a stator tip strip, wherein the stator tipstrip is disposed proximate the rotor; a first steam source injectedinto the bowl region at a first temperature; a packing head disposedproximate the stator tip strip; a rotor cooling steam source injected ata second temperature along a path in close proximity to the rotor,wherein the second temperature is lower than the first temperature; anda flex seal having a fixed portion and a free portion, wherein the flexseal is fixedly coupled at the fixed portion to at least one of thestator assembly, the packing head and the stator tip strip, wherein theflex seal prevents the first steam source from entering the path inclose proximity to the rotor.
 11. The seal of claim 10, wherein the flexseal is disposed in an intermediate pressure section of the steamturbine system.
 12. The seal of claim 10, wherein the fixed portion isbolted to the tip strip.
 13. The seal of claim 10, wherein the fixedportion is riveted to the tip strip.
 14. The seal of claim 10, whereinthe fixed portion is welded to the packing head.
 15. The seal of claim10, further comprising an axial direction and a radial direction,wherein the axial direction relatively corresponds to a longitudinaldirection of the rotor and the radial direction relatively extends fromthe rotor to an outer casing.
 16. The seal of a claim 15, wherein thefree portion of the flex seal is configured to be displaced in the axialdirection and the radial direction.
 17. The seal of claim 10, whereinthe flex seal is of a relatively Y-shaped geometric configuration.
 18. Aseal for a steam turbine system comprising: an intermediate pressuresection having a rotor, a bowl region, an outer casing and a statorassembly having a tip strip disposed proximate the rotor, wherein theintermediate pressure section comprises an axial direction correspondingto a longitudinal direction of the rotor and a radial directionextending relatively from the rotor to the outer casing; a packing headdisposed proximate the tip strip; and a flex seal having a first endportion fixedly secured to at least one of the tip strip and the packinghead, with a second end portion slidably engaged with at least one ofthe tip strip and the packing head and configured to be displaced in theaxial direction and the radial direction.
 19. The seal of claim 18,further comprising: a first steam source injected into the bowl regionat a first temperature; a rotor cooling steam source injected at asecond temperature along a path in close proximity to the rotor, whereinthe second temperature is lower than the first temperature, wherein theflex seal prevents the first steam source from entering the path inclose proximity to the rotor.
 20. The seal of claim 18, wherein the flexseal is of a relatively Y-shaped geometric configuration.